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PICList Thread
'[PIC]: FCC question'
2002\06\12@145904 by Drew Vassallo

picon face
The latest thread regarding FCC compliance got me thinking.  I'm about to
start on producing my first commercial product (100% developed and produced
by me, that is), which is intended for the model airplane (hobby) industry.
I hope to produce at least a few hundred per year.

Basically it's an in-flight monitor (no RF or telemetry) that stores
measured values of altitude, etc.  The unit operates at 4 MHz and borrows
power from the flight battery pack of the radio control.  (I don't know if
any of this matters, but I'm including it for information.)

Do I have to be concerned about FCC compliance for this application?  That
is, do I have to have this formally certified in order to sell it
commercially?  Does it need some sort of markings on the package that
indicate compliance?  Or can I just "let the buyer beware" so to speak?  I
feel that this is a relatively innocuous application, and this isn't going
to cause problems with the radio controls (they typically operate in the 72
KHz range), as I've tested it on a number of airplanes using various radios.

--Andrew

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2002\06\12@160317 by Harold M Hallikainen

picon face
       Have a look at
http://www.hallikainen.org/cgi-bin/section.pl?section=15.103 for exempt
devices. This may even be exempt as being in an aircraft (though a small
one). If you can get the clock down to under 1.705 MHz and operate on
batteries, it's also exempt. You are exempted from labeling under
http://www.hallikainen.org/cgi-bin/section.pl?section=15.105 if you are
exempt under 15.103.

Harold


On Wed, 12 Jun 2002 18:56:56 +0000 Drew Vassallo <spam_OUTsnurpleTakeThisOuTspamHOTMAIL.COM>
writes:
{Quote hidden}

FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com

Reach broadcasters, engineers, manufacturers, compliance labs, and
attorneys.
Advertise at http://www.hallikainen.com/FccRules/ .


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2002\06\12@160724 by Pic Dude

flavicon
face
Been reading the gobs of FCC part 15 docs this past weekend
and will summarize eventually after I've read all the relevant
parts.  However, I can add a few clues.  Experts feel free
to chime in and correct me if necessary.

If your device does not purposely generate RF signals, it is
classified as an unintentional radiator.  There are standards
to be met, but there are exemptions available for various
devices.  (Exempt from having the device tested/certified --
this does not mean that you are exempt from creating emissions
beyond a certain level).  There are exemptions for battery
operated devices not consuming more than some ridiculously
low level of power (IIRC 6nW), and digital devices operating
below 1.705MHz.  There is also an exemption for devices in a
transportation vehicle (car or airplane), but I'm not sure if
an RC airplane classifies as true transportation.  Unless you
promise to deliver something everytime you fly it :-)

There is also special situations for items sold as kits -- so
perhaps that might meet your requirements.

Labelling pretty much needs to say that it meets FCC part 15
standards.  Also, the rules are written as if they're nice
about it -- if it's found that your device emits more than the
limit of emissions, then you get a slap on the wrist, and meet
the compliance requirements.

Obviously lots of paraphrasing here, so these are really just
clues.  I recommend you read part 15 for yourself.

Cheers,
-Neil.




{Original Message removed}

2002\06\12@210505 by mluvara

picon face
I think you may have made a typo, but R/C aircraft models are on 72MHz in
the US, not kHz range. Your device should fall under the unintentional
radiator area and I believe, unless you can find some loophole, technically
you are required to meet the emissions criteria for FCC. If you send it
into other countries, well be prepared for another barage of tests as they
generally require immunity, meaning that it has to be immune to ESD
(electrostatic discharge), emissions off of the signal lines themselves,
etc etc etc. Generally, you need to test to the fifth harmonic of the
highest clock frequency. Well, in your case, looks like 20MHz, but the
radiated emissions (measured with an antenna) start at 30MHz.

I'm developing a telemetry unit myself for the R/C hobby industry, but it
will have an intentional radiator, so will need to meet FCC, etc.

I'll let you find out more when I do. I have to dig into the standards at
work because I deal with things in the field like this there, but are not
sure of some of the exemptions that may fall into this area. But, R/C
receivers in the plane are FCC part 15 compliant. You don't want to
interfere with them, so the FCC may regulate that you have a product
checked.

Take a look at some of these links. It will give you an idea of the
standards by country.

http://www.ul.com/emc/
http://www.ul.com/emc/emcfaq1.html
In the Q&A section, look at "What are the EMC laws in the United States? "
http://www.ul.com/emc/emcacc.html

http://www.baclcorp.com/Test_services.htm
www.baclcorp.com/certification_process.htm
http://www.baclcorp.com/tcb_info.htm

Hopefully, this helps some.

Michael


> [Original Message]
> From: Drew Vassallo <.....snurpleKILLspamspam@spam@HOTMAIL.COM>
> To: <PICLISTspamKILLspamMITVMA.MIT.EDU>
> Date: 6/12/02 11:56:56 AM
> Subject: [PIC]: FCC question
>
> The latest thread regarding FCC compliance got me thinking.  I'm about to
> start on producing my first commercial product (100% developed and
produced
> by me, that is), which is intended for the model airplane (hobby)
industry.
{Quote hidden}

72
> KHz range), as I've tested it on a number of airplanes using various
radios.
>
> --Andrew
>
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- Michael Luvara

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2002\06\12@220627 by Drew Vassallo

picon face
>I think you may have made a typo, but R/C aircraft models are on 72MHz in
>the US, not kHz range.

Yeah, it was an unthinking typo.  I did in fact mean to type "KHz" but I
wasn't thinking about the actual frequency, which obviously is MHz, as you
stated.

I think I might instead try to go the other way and simply drop the
frequency down to 1 MHz for the circuit.  It doesn't necessarily HAVE To
function at 4 MHz.  In fact, it'll just drop some of the delay values that I
have and increase the A/D cycles, that's all.  I'll have to check the
datasheets to make sure I don't have to change crystal capacitors.

According to PIC Dude, a frequency of 1 MHz should be low enough to fall
into the "exempt" category, though I haven't checked that fact for myself
yet.

--Andrew

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2002\06\12@221303 by Pic Dude

flavicon
face
There are other little bits and pieces too, other than the
1Mhz req.  See 15.103 for specifics.

BTW, I wanted to use a 1Mhz on the petfeeder, but the
odd thing is that digikey lists these for $7+ ea, while
131.072khz, and 4MHz crystals are approx $2 ea.

What gives?





{Original Message removed}

2002\06\12@223037 by Drew Vassallo

picon face
>BTW, I wanted to use a 1Mhz on the petfeeder, but the
>odd thing is that digikey lists these for $7+ ea, while
>131.072khz, and 4MHz crystals are approx $2 ea.

What price sheet you lookin' at??

I can get a 4 MHz ECS xtal HC-49/UA size for $.64 in single piece quantities
from Digi-Key.

A 131.072 KHz Epson (cylindrical) goes for $1.77 each.

Both are thru-hole parts.

I did notice, however, that 1 MHz crystals are INSANELY expensive.  Up to
$17 for an ECS crystal.

Maybe I'll have to use a resonator or even just go to an RC... my timing
requirements are very loose.

--Andrew

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2002\06\12@224543 by Drew Vassallo

picon face
Which brings up another point:

I've been using 1/(2*pi*R*C) to determine the PIC frequency using an RC
oscillator circuit.  Not being an EE, I'm not sure if this is entirely
correct, but it seems to be in agreement with what I see happening with the
PIC when I use it in my application.

Anything wrong with doing it this way?

e.g., an 18pF cap with (2) 4.7Kohm resistors in series gives me
approximately 4.25us per cycle, or 941 KHz input frequency, at least by my
calculations.

Please correct me if I'm mistaken.

--Andrew

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2002\06\13@003747 by Pic Dude

flavicon
face
The 131.072 f/$1.77 is the one I am using (I just rounded
off to $2).  I hadn't run across the $0.64 4-mhz units,
but that doesn't solve my problem, as I'm also trying to
stay within the FCC 1.705Mhz limit.  1-Mhz is what I
really need or even 1.544Mhz.

Cheers,
-Neil.



{Original Message removed}

2002\06\13@042715 by Alan B. Pearce

face picon face
It would probably pay to do some basic RF shielding things anyway. I was
originally thinking in terms of putting your device into something like a
metal film can, you know those aluminium cans 35mm flim used to come in, but
these are hard to come by these days, and the weight penalty is probably a
bit much. However you may achieve similar shielding by wrapping it in a
single layer of duct tape or similar metal adhesive tape. This should
minimise any radiation without too big a weight penalty.

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2002\06\13@043109 by Alan B. Pearce

face picon face
>BTW, I wanted to use a 1Mhz on the petfeeder, but the
>odd thing is that digikey lists these for $7+ ea, while
>131.072khz, and 4MHz crystals are approx $2 ea.

I believe there is manufacturing hassles at around the 1MHz area. I am not
really sure what they are, but I suspect that it is a point where you cross
between two different modes of operation of the crystal physical vibration.
I remember when the HF Marine bands went to SSB the company I worked for
designed a receiver using a 1.4MHz filter, and had a horrible job getting
crystal filters for it, because the crystals were right in a difficult to
process frequency range.

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2002\06\13@084621 by Olin Lathrop

face picon face
> I've been using 1/(2*pi*R*C) to determine the PIC frequency using an RC
> oscillator circuit.  Not being an EE, I'm not sure if this is entirely
> correct, but it seems to be in agreement with what I see happening with
the
> PIC when I use it in my application.

1/(2*Pi*R*C) is the frequency at which the magnitude of the impedence of the
resistor and capacitor match.  In most circuits, this is therefore roughly
the frequency at which "things start to happen" either above or below that
frequency.  At much higher frequencies, the capacitor looks like a short
compared to the resistor, and at much lower frequencies the capacitor looks
like an open circuit compared to the resistor.  This is also the "rolloff"
frequency of a simple R-C filter.  However, this will only give you a rough
idea of the likely frequency of an unknown oscillator circuit.  There is no
guarantee that the circuit is designed to oscillate at that point.


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2002\06\13@092024 by Mark J. Dulcey

flavicon
face
Pic Dude wrote:
> The 131.072 f/$1.77 is the one I am using (I just rounded
> off to $2).  I hadn't run across the $0.64 4-mhz units,
> but that doesn't solve my problem, as I'm also trying to
> stay within the FCC 1.705Mhz limit.  1-Mhz is what I
> really need or even 1.544Mhz.

You're right - the 1 MHz crystals from Digi-Key are indeed horribly
expensive. You can do better elsewhere - about $5 at Jameco, for example
- but that's still steep. On the other hand, a 1 MHz oscillator MODULE
isn't all that bad - about $3 at Digi-Key, or $2.24 at Mouser - so that
might be the way to go. Besides, it gets you back an I/O pin on some
PICs; with an external clock, you need only one pin instead of two.

There are two reasons that 1 MHz crystals are expensive. First is that,
due to physical constraints, it's a difficult frequency to make a
crystal for; you need a big chunk of quartz. (The huge 100 KHz crystals
that used to be used in calibrator circuits had the same issues, but
magnified. The tiny 32 KHz crystals that you see nowadays use a
different mode of operation that isn't suitable for a frequency as high
as 1 MHz.) Second is that they are mostly made for calibration circuits,
so the crystals that you can get are mostly high-precision parts, and
you're paying extra for that.

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2002\06\13@093010 by Gordon Varney

flavicon
face
Andrew,
       Been there did that....... The formula you are using is correct for a different application. Microchip has not spec'ed
a formula for this purpose. The RC formula does not apply here. The OSC is mostly frequency dependant on the resister.
The capacitor plays less of a role in deterring the frequency. It is used more for stability and the charge cycle.
However you must have it. To solve for frequency you must try it imperially. Others may be able to tell you what values
they used to get the frequency they wanted.

Gordon Varney
http://www.iamnee.com

{Quote hidden}

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2002\06\13@111254 by Pic Dude

flavicon
face
In my sleep last night I was trying to devise a system
running 2 clocks -- the pic would run in a basic RC
system setup for about 1 MHz, and that would handle all
the display and other perihperal stuff; and I'd use an
external oscillator at any low frequency (32.788 or less
if available) to generate the 1hz signals for the clock.
This would have to be sent to the external interrupt
pin.

However, AFAIK (w/o looking at docs), I can't assign a
pre-scaler to that interrupt, so it seems like I'd get
way more interrupts than I need and it seems wasteful,
and may cause some confusion during EEPROM writes, etc.

Yes, I'm avoiding using external freq dividers.  Need to
think and research some more about this one...

Cheers,
-Neil.



{Original Message removed}

2002\06\13@114342 by Pic Dude

flavicon
face
Just searched for both of these and found them.  $2.24 is not
too bad I guess.

Cheers,
-Neil.




-----Original Message-----
From: pic microcontroller discussion list
[.....PICLISTKILLspamspam.....MITVMA.MIT.EDU]On Behalf Of Mark J. Dulcey
Sent: Thursday, June 13, 2002 6:22 AM
To: EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU
Subject: Re: [PIC]: FCC question


Pic Dude wrote:
> The 131.072 f/$1.77 is the one I am using (I just rounded
> off to $2).  I hadn't run across the $0.64 4-mhz units,
> but that doesn't solve my problem, as I'm also trying to
> stay within the FCC 1.705Mhz limit.  1-Mhz is what I
> really need or even 1.544Mhz.

You're right - the 1 MHz crystals from Digi-Key are indeed horribly
expensive. You can do better elsewhere - about $5 at Jameco, for example
- but that's still steep. On the other hand, a 1 MHz oscillator MODULE
isn't all that bad - about $3 at Digi-Key, or $2.24 at Mouser - so that
might be the way to go. Besides, it gets you back an I/O pin on some
PICs; with an external clock, you need only one pin instead of two.

There are two reasons that 1 MHz crystals are expensive. First is that,
due to physical constraints, it's a difficult frequency to make a
crystal for; you need a big chunk of quartz. (The huge 100 KHz crystals
that used to be used in calibrator circuits had the same issues, but
magnified. The tiny 32 KHz crystals that you see nowadays use a
different mode of operation that isn't suitable for a frequency as high
as 1 MHz.) Second is that they are mostly made for calibration circuits,
so the crystals that you can get are mostly high-precision parts, and
you're paying extra for that.

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2002\06\13@114351 by Michael Rigby-Jones

flavicon
face
{Quote hidden}

Don't know which PIC you are using but the bigger ones with timer 1 have
provision for a second crystal to drive  timer 1.  If not you could use an
external oscillator and drive TMR0 and intterupt on overflow .  32.768Khz
needs to be divided by 2^15 to get 1 second, so setting TMR0 pre-sclaer to
1:128 and interrupting on rollover (1:256) would give exactly 1 second
interrupts.

Regards

Mike

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2002\06\13@115211 by Bob Ammerman

picon face
The 16F87x chips (and others IIRC) include a separate low-power oscillator
designed to run off a cheap 32Khz or similar low-speed XTAL.

This osc then clocks timer 1, which can be used as a divider so that it only
interrupts and wakes up the PIC every so often.

Bob Ammerman
RAm Systems


----- Original Message -----
From: "Pic Dude" <KILLspampicdudeKILLspamspamAVN-TECH.COM>
To: <RemoveMEPICLISTTakeThisOuTspamMITVMA.MIT.EDU>
Sent: Thursday, June 13, 2002 11:11 AM
Subject: Re: [PIC]: FCC question


{Quote hidden}

> {Original Message removed}

2002\06\13@122336 by Pic Dude

flavicon
face
Using a 16F872, but not familiar with being able to
use a second crystal to drive TMR1.  I'll hit the
datasheet again after this.

Think you're missing a bit of context -- The 32.768 is
fine and easily divided to 1 sec, but I need something
higher to multiplex the displays w/o flickering.

131.072khz still has a bit of flicker, 1Mhz crystals
are waaayyy higher in price, and above 1.705Mhz there
are FCC regs to be worried about.

Thanks,
-Neil.



{Original Message removed}

2002\06\13@125621 by Harold M Hallikainen

picon face
       I did something like this with a 16F870. There's a 32 kHz crystal on the
timer 1 oscillator on the chip. Something like every 1.6 seconds (if I
recall correctly), the timer overflows and wakes the chip up. It then
runs at 4 MHz, does stuff, then goes back to sleep.
       Also, the 18C452 (and similar) has a clock switch so you can switch the
processor core between two speeds. I haven't used it, but it's
interesting...

Harold

On Thu, 13 Jun 2002 10:11:52 -0500 Pic Dude <spamBeGonepicdudespamBeGonespamAVN-TECH.COM>
writes:
{Quote hidden}

> {Original Message removed}

2002\06\13@132107 by M. Adam Davis

flavicon
face
How large/what kind of a display are you multiplexing?  You don't need
to update it very often (30-60 times per second).  You have over 8000
instructions/second to update it and do your other work.  If it's
7-segment LED than each segment shouldn't take more than 5-10
instruction cycles to update, fewer with good design.  Of course this
also depends on how your data to be displayed is stored...

-Adam

Pic Dude wrote:

{Quote hidden}

>{Original Message removed}

2002\06\13@153436 by miked

flavicon
face
EMS/Jomar sells just such a thing. I didn't look for an FCC sticker at Toledo.
http://www.emsjomar.com/main-0.htm
>
> The latest thread regarding FCC compliance got me thinking.  I'm about to
> start on producing my first commercial product (100% developed and
> produced by me, that is), which is intended for the model airplane (hobby)
> industry. I hope to produce at least a few hundred per year.
>
> Basically it's an in-flight monitor (no RF or telemetry) that stores
> measured values of altitude, etc.  The unit operates at 4 MHz and borrows
> power from the flight battery pack of the radio control.  (I don't know if
> any of this matters, but I'm including it for information.)
>
> Do I have to be concerned about FCC compliance for this application?  That
> is, do I have to have this formally certified in order to sell it
> commercially?  Does it need some sort of markings on the package that
> indicate compliance?


Michiana R/C Choppers
http://www.mrcc.info
TakeThisOuTmikedEraseMEspamspam_OUTmrcc.info

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2002\06\14@064335 by Peter L. Peres

picon face
On Wed, 12 Jun 2002, Pic Dude wrote:

>There are other little bits and pieces too, other than the
>1Mhz req.  See 15.103 for specifics.
>
>BTW, I wanted to use a 1Mhz on the petfeeder, but the
>odd thing is that digikey lists these for $7+ ea, while
>131.072khz, and 4MHz crystals are approx $2 ea.
>
>What gives?

1MHz is fairly rarely used and it could be a special cut. You need to
order a special-cut crystal to realise just how cheap $7 is ...

Anyway when I have something really slow to do (like clocks and such) I
try to do them using 32kHz crystals. I have made two timers so far that
used 50Hz as clock (12C508).

Peter

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2002\06\17@124047 by miked
flavicon
face
Resources Unlimited, http://www.resunltd4u.com/ has 1Mhz
oscillators (DIP can type) 4 for $2. OSC1MHZ-4

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